Réponse :
Explications étape par étape :
■ cos(5π/4) = cos(4π/4 + π/4) = cos(π + π/4)
= - cos(π/4) = -√2/2 ≈ -0,7071
■ sin(5π/4) = -√2/2 aussi !
■ cos(5π/6) = cos(π - π/6) = -cos(π/6) = -√3/2 ≈ -0,866
■ sin(7π/6) = sin(π + π/6) = - sin(π/6) = -1/2 = -0,5